1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * PowerPC Memory Protection Keys management
4 *
5 * Copyright 2017, Ram Pai, IBM Corporation.
6 */
7
8 #include <asm/mman.h>
9 #include <asm/mmu_context.h>
10 #include <asm/mmu.h>
11 #include <asm/setup.h>
12 #include <asm/smp.h>
13 #include <asm/firmware.h>
14
15 #include <linux/pkeys.h>
16 #include <linux/of_fdt.h>
17
18
19 int num_pkey; /* Max number of pkeys supported */
20 /*
21 * Keys marked in the reservation list cannot be allocated by userspace
22 */
23 u32 reserved_allocation_mask __ro_after_init;
24
25 /* Bits set for the initially allocated keys */
26 static u32 initial_allocation_mask __ro_after_init;
27
28 /*
29 * Even if we allocate keys with sys_pkey_alloc(), we need to make sure
30 * other thread still find the access denied using the same keys.
31 */
32 u64 default_amr __ro_after_init = ~0x0UL;
33 u64 default_iamr __ro_after_init = 0x5555555555555555UL;
34 u64 default_uamor __ro_after_init;
35 EXPORT_SYMBOL(default_amr);
36 /*
37 * Key used to implement PROT_EXEC mmap. Denies READ/WRITE
38 * We pick key 2 because 0 is special key and 1 is reserved as per ISA.
39 */
40 static int execute_only_key = 2;
41 static bool pkey_execute_disable_supported;
42
43
44 #define AMR_BITS_PER_PKEY 2
45 #define AMR_RD_BIT 0x1UL
46 #define AMR_WR_BIT 0x2UL
47 #define IAMR_EX_BIT 0x1UL
48 #define PKEY_REG_BITS (sizeof(u64) * 8)
49 #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY))
50
dt_scan_storage_keys(unsigned long node,const char * uname,int depth,void * data)51 static int __init dt_scan_storage_keys(unsigned long node,
52 const char *uname, int depth,
53 void *data)
54 {
55 const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
56 const __be32 *prop;
57 int *pkeys_total = (int *) data;
58
59 /* We are scanning "cpu" nodes only */
60 if (type == NULL || strcmp(type, "cpu") != 0)
61 return 0;
62
63 prop = of_get_flat_dt_prop(node, "ibm,processor-storage-keys", NULL);
64 if (!prop)
65 return 0;
66 *pkeys_total = be32_to_cpu(prop[0]);
67 return 1;
68 }
69
scan_pkey_feature(void)70 static int __init scan_pkey_feature(void)
71 {
72 int ret;
73 int pkeys_total = 0;
74
75 /*
76 * Pkey is not supported with Radix translation.
77 */
78 if (early_radix_enabled())
79 return 0;
80
81 ret = of_scan_flat_dt(dt_scan_storage_keys, &pkeys_total);
82 if (ret == 0) {
83 /*
84 * Let's assume 32 pkeys on P8/P9 bare metal, if its not defined by device
85 * tree. We make this exception since some version of skiboot forgot to
86 * expose this property on power8/9.
87 */
88 if (!firmware_has_feature(FW_FEATURE_LPAR)) {
89 unsigned long pvr = mfspr(SPRN_PVR);
90
91 if (PVR_VER(pvr) == PVR_POWER8 || PVR_VER(pvr) == PVR_POWER8E ||
92 PVR_VER(pvr) == PVR_POWER8NVL || PVR_VER(pvr) == PVR_POWER9)
93 pkeys_total = 32;
94 }
95 }
96
97 #ifdef CONFIG_PPC_MEM_KEYS
98 /*
99 * Adjust the upper limit, based on the number of bits supported by
100 * arch-neutral code.
101 */
102 pkeys_total = min_t(int, pkeys_total,
103 ((ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) + 1));
104 #endif
105 return pkeys_total;
106 }
107
pkey_early_init_devtree(void)108 void __init pkey_early_init_devtree(void)
109 {
110 int pkeys_total, i;
111
112 #ifdef CONFIG_PPC_MEM_KEYS
113 /*
114 * We define PKEY_DISABLE_EXECUTE in addition to the arch-neutral
115 * generic defines for PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE.
116 * Ensure that the bits a distinct.
117 */
118 BUILD_BUG_ON(PKEY_DISABLE_EXECUTE &
119 (PKEY_DISABLE_ACCESS | PKEY_DISABLE_WRITE));
120
121 /*
122 * pkey_to_vmflag_bits() assumes that the pkey bits are contiguous
123 * in the vmaflag. Make sure that is really the case.
124 */
125 BUILD_BUG_ON(__builtin_clzl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT) +
126 __builtin_popcountl(ARCH_VM_PKEY_FLAGS >> VM_PKEY_SHIFT)
127 != (sizeof(u64) * BITS_PER_BYTE));
128 #endif
129 /*
130 * Only P7 and above supports SPRN_AMR update with MSR[PR] = 1
131 */
132 if (!early_cpu_has_feature(CPU_FTR_ARCH_206))
133 return;
134
135 /* scan the device tree for pkey feature */
136 pkeys_total = scan_pkey_feature();
137 if (!pkeys_total)
138 goto out;
139
140 /* Allow all keys to be modified by default */
141 default_uamor = ~0x0UL;
142
143 cur_cpu_spec->mmu_features |= MMU_FTR_PKEY;
144
145 /*
146 * The device tree cannot be relied to indicate support for
147 * execute_disable support. Instead we use a PVR check.
148 */
149 if (pvr_version_is(PVR_POWER7) || pvr_version_is(PVR_POWER7p))
150 pkey_execute_disable_supported = false;
151 else
152 pkey_execute_disable_supported = true;
153
154 #ifdef CONFIG_PPC_4K_PAGES
155 /*
156 * The OS can manage only 8 pkeys due to its inability to represent them
157 * in the Linux 4K PTE. Mark all other keys reserved.
158 */
159 num_pkey = min(8, pkeys_total);
160 #else
161 num_pkey = pkeys_total;
162 #endif
163
164 if (unlikely(num_pkey <= execute_only_key) || !pkey_execute_disable_supported) {
165 /*
166 * Insufficient number of keys to support
167 * execute only key. Mark it unavailable.
168 */
169 execute_only_key = -1;
170 } else {
171 /*
172 * Mark the execute_only_pkey as not available for
173 * user allocation via pkey_alloc.
174 */
175 reserved_allocation_mask |= (0x1 << execute_only_key);
176
177 /*
178 * Deny READ/WRITE for execute_only_key.
179 * Allow execute in IAMR.
180 */
181 default_amr |= (0x3ul << pkeyshift(execute_only_key));
182 default_iamr &= ~(0x1ul << pkeyshift(execute_only_key));
183
184 /*
185 * Clear the uamor bits for this key.
186 */
187 default_uamor &= ~(0x3ul << pkeyshift(execute_only_key));
188 }
189
190 if (unlikely(num_pkey <= 3)) {
191 /*
192 * Insufficient number of keys to support
193 * KUAP/KUEP feature.
194 */
195 disable_kuep = true;
196 disable_kuap = true;
197 WARN(1, "Disabling kernel user protection due to low (%d) max supported keys\n", num_pkey);
198 } else {
199 /* handle key which is used by kernel for KAUP */
200 reserved_allocation_mask |= (0x1 << 3);
201 /*
202 * Mark access for kup_key in default amr so that
203 * we continue to operate with that AMR in
204 * copy_to/from_user().
205 */
206 default_amr &= ~(0x3ul << pkeyshift(3));
207 default_iamr &= ~(0x1ul << pkeyshift(3));
208 default_uamor &= ~(0x3ul << pkeyshift(3));
209 }
210
211 /*
212 * Allow access for only key 0. And prevent any other modification.
213 */
214 default_amr &= ~(0x3ul << pkeyshift(0));
215 default_iamr &= ~(0x1ul << pkeyshift(0));
216 default_uamor &= ~(0x3ul << pkeyshift(0));
217 /*
218 * key 0 is special in that we want to consider it an allocated
219 * key which is preallocated. We don't allow changing AMR bits
220 * w.r.t key 0. But one can pkey_free(key0)
221 */
222 initial_allocation_mask |= (0x1 << 0);
223
224 /*
225 * key 1 is recommended not to be used. PowerISA(3.0) page 1015,
226 * programming note.
227 */
228 reserved_allocation_mask |= (0x1 << 1);
229 default_uamor &= ~(0x3ul << pkeyshift(1));
230
231 /*
232 * Prevent the usage of OS reserved keys. Update UAMOR
233 * for those keys. Also mark the rest of the bits in the
234 * 32 bit mask as reserved.
235 */
236 for (i = num_pkey; i < 32 ; i++) {
237 reserved_allocation_mask |= (0x1 << i);
238 default_uamor &= ~(0x3ul << pkeyshift(i));
239 }
240 /*
241 * Prevent the allocation of reserved keys too.
242 */
243 initial_allocation_mask |= reserved_allocation_mask;
244
245 pr_info("Enabling pkeys with max key count %d\n", num_pkey);
246 out:
247 /*
248 * Setup uamor on boot cpu
249 */
250 mtspr(SPRN_UAMOR, default_uamor);
251
252 return;
253 }
254
255 #ifdef CONFIG_PPC_KUEP
setup_kuep(bool disabled)256 void setup_kuep(bool disabled)
257 {
258 if (disabled)
259 return;
260 /*
261 * On hash if PKEY feature is not enabled, disable KUAP too.
262 */
263 if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
264 return;
265
266 if (smp_processor_id() == boot_cpuid) {
267 pr_info("Activating Kernel Userspace Execution Prevention\n");
268 cur_cpu_spec->mmu_features |= MMU_FTR_BOOK3S_KUEP;
269 }
270
271 /*
272 * Radix always uses key0 of the IAMR to determine if an access is
273 * allowed. We set bit 0 (IBM bit 1) of key0, to prevent instruction
274 * fetch.
275 */
276 mtspr(SPRN_IAMR, AMR_KUEP_BLOCKED);
277 isync();
278 }
279 #endif
280
281 #ifdef CONFIG_PPC_KUAP
setup_kuap(bool disabled)282 void setup_kuap(bool disabled)
283 {
284 if (disabled)
285 return;
286 /*
287 * On hash if PKEY feature is not enabled, disable KUAP too.
288 */
289 if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))
290 return;
291
292 if (smp_processor_id() == boot_cpuid) {
293 pr_info("Activating Kernel Userspace Access Prevention\n");
294 cur_cpu_spec->mmu_features |= MMU_FTR_KUAP;
295 }
296
297 /*
298 * Set the default kernel AMR values on all cpus.
299 */
300 mtspr(SPRN_AMR, AMR_KUAP_BLOCKED);
301 isync();
302 }
303 #endif
304
305 #ifdef CONFIG_PPC_MEM_KEYS
pkey_mm_init(struct mm_struct * mm)306 void pkey_mm_init(struct mm_struct *mm)
307 {
308 if (!mmu_has_feature(MMU_FTR_PKEY))
309 return;
310 mm_pkey_allocation_map(mm) = initial_allocation_mask;
311 mm->context.execute_only_pkey = execute_only_key;
312 }
313
init_amr(int pkey,u8 init_bits)314 static inline void init_amr(int pkey, u8 init_bits)
315 {
316 u64 new_amr_bits = (((u64)init_bits & 0x3UL) << pkeyshift(pkey));
317 u64 old_amr = current_thread_amr() & ~((u64)(0x3ul) << pkeyshift(pkey));
318
319 current->thread.regs->amr = old_amr | new_amr_bits;
320 }
321
init_iamr(int pkey,u8 init_bits)322 static inline void init_iamr(int pkey, u8 init_bits)
323 {
324 u64 new_iamr_bits = (((u64)init_bits & 0x1UL) << pkeyshift(pkey));
325 u64 old_iamr = current_thread_iamr() & ~((u64)(0x1ul) << pkeyshift(pkey));
326
327 if (!likely(pkey_execute_disable_supported))
328 return;
329
330 current->thread.regs->iamr = old_iamr | new_iamr_bits;
331 }
332
333 /*
334 * Set the access rights in AMR IAMR and UAMOR registers for @pkey to that
335 * specified in @init_val.
336 */
__arch_set_user_pkey_access(struct task_struct * tsk,int pkey,unsigned long init_val)337 int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
338 unsigned long init_val)
339 {
340 u64 new_amr_bits = 0x0ul;
341 u64 new_iamr_bits = 0x0ul;
342 u64 pkey_bits, uamor_pkey_bits;
343
344 /*
345 * Check whether the key is disabled by UAMOR.
346 */
347 pkey_bits = 0x3ul << pkeyshift(pkey);
348 uamor_pkey_bits = (default_uamor & pkey_bits);
349
350 /*
351 * Both the bits in UAMOR corresponding to the key should be set
352 */
353 if (uamor_pkey_bits != pkey_bits)
354 return -EINVAL;
355
356 if (init_val & PKEY_DISABLE_EXECUTE) {
357 if (!pkey_execute_disable_supported)
358 return -EINVAL;
359 new_iamr_bits |= IAMR_EX_BIT;
360 }
361 init_iamr(pkey, new_iamr_bits);
362
363 /* Set the bits we need in AMR: */
364 if (init_val & PKEY_DISABLE_ACCESS)
365 new_amr_bits |= AMR_RD_BIT | AMR_WR_BIT;
366 else if (init_val & PKEY_DISABLE_WRITE)
367 new_amr_bits |= AMR_WR_BIT;
368
369 init_amr(pkey, new_amr_bits);
370 return 0;
371 }
372
execute_only_pkey(struct mm_struct * mm)373 int execute_only_pkey(struct mm_struct *mm)
374 {
375 return mm->context.execute_only_pkey;
376 }
377
vma_is_pkey_exec_only(struct vm_area_struct * vma)378 static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
379 {
380 /* Do this check first since the vm_flags should be hot */
381 if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
382 return false;
383
384 return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
385 }
386
387 /*
388 * This should only be called for *plain* mprotect calls.
389 */
__arch_override_mprotect_pkey(struct vm_area_struct * vma,int prot,int pkey)390 int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
391 int pkey)
392 {
393 /*
394 * If the currently associated pkey is execute-only, but the requested
395 * protection is not execute-only, move it back to the default pkey.
396 */
397 if (vma_is_pkey_exec_only(vma) && (prot != PROT_EXEC))
398 return 0;
399
400 /*
401 * The requested protection is execute-only. Hence let's use an
402 * execute-only pkey.
403 */
404 if (prot == PROT_EXEC) {
405 pkey = execute_only_pkey(vma->vm_mm);
406 if (pkey > 0)
407 return pkey;
408 }
409
410 /* Nothing to override. */
411 return vma_pkey(vma);
412 }
413
pkey_access_permitted(int pkey,bool write,bool execute)414 static bool pkey_access_permitted(int pkey, bool write, bool execute)
415 {
416 int pkey_shift;
417 u64 amr;
418
419 pkey_shift = pkeyshift(pkey);
420 if (execute)
421 return !(current_thread_iamr() & (IAMR_EX_BIT << pkey_shift));
422
423 amr = current_thread_amr();
424 if (write)
425 return !(amr & (AMR_WR_BIT << pkey_shift));
426
427 return !(amr & (AMR_RD_BIT << pkey_shift));
428 }
429
arch_pte_access_permitted(u64 pte,bool write,bool execute)430 bool arch_pte_access_permitted(u64 pte, bool write, bool execute)
431 {
432 if (!mmu_has_feature(MMU_FTR_PKEY))
433 return true;
434
435 return pkey_access_permitted(pte_to_pkey_bits(pte), write, execute);
436 }
437
438 /*
439 * We only want to enforce protection keys on the current thread because we
440 * effectively have no access to AMR/IAMR for other threads or any way to tell
441 * which AMR/IAMR in a threaded process we could use.
442 *
443 * So do not enforce things if the VMA is not from the current mm, or if we are
444 * in a kernel thread.
445 */
arch_vma_access_permitted(struct vm_area_struct * vma,bool write,bool execute,bool foreign)446 bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
447 bool execute, bool foreign)
448 {
449 if (!mmu_has_feature(MMU_FTR_PKEY))
450 return true;
451 /*
452 * Do not enforce our key-permissions on a foreign vma.
453 */
454 if (foreign || vma_is_foreign(vma))
455 return true;
456
457 return pkey_access_permitted(vma_pkey(vma), write, execute);
458 }
459
arch_dup_pkeys(struct mm_struct * oldmm,struct mm_struct * mm)460 void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
461 {
462 if (!mmu_has_feature(MMU_FTR_PKEY))
463 return;
464
465 /* Duplicate the oldmm pkey state in mm: */
466 mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
467 mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;
468 }
469
470 #endif /* CONFIG_PPC_MEM_KEYS */
471